1. Field of the Invention
The invention relates to a device for deriving a clock signal having a specific frequency from a synchronizing signal derived from an electrical signal, for example, a video signal, the device comprising
an input terminal for receiving the synchronizing signal, PA1 a phase comparator having a first input coupled to the input terminal, a second input and an output, PA1 a voltage controlled oscillator having an input coupled to the output of the phase comparator, and an output, PA1 counter means having a first input coupled to the output of the voltage controlled oscillator, a second input for receiving a preset control signal, and an output coupled to the second input of the phase comparator, PA1 preset control signal generator means having an input coupled to the input terminal and an output coupled to the second input of the counter means, the counter means being adapted to set its count value to a preset value in response to the preset control signal applied to its preset control signal input, and to a videorecorder provided with the device. PA1 window signal generator means for determining a window signal in response to a specified count value of the counter means, PA1 detector means for detecting whether at least one edge in the synchronizing signal falls outside a time interval defined by the window signal and for generating said preset control signal in response to said detection, said detector means having an input coupled to the input of the preset control signal generator means and an output coupled to the output of said preset control signal generator means.
2. Description of the Related Art
A device as defined in the opening paragraph is known from U.S. Pat. No. 5,043,966 (PHN 12.569) and enables the derivation of a clock signal from a synchronizing signal that is affected with time-base errors. In the known device, the head switch impulse is used to derive the preset control signal.